How Linux is built with Greg Kroah-Hartman

Linux is the most widespread operating system, globally – but how is it built? Few people are better to answer this than Greg Kroah-Hartman: a Linux kernel maintainer for 25 years, and one of the 3 Linux Kernel Foundation Fellows (the other two are Linus Torvalds and Shuah Khan). Greg manages the Linux kernel’s stable releases, and is a maintainer of multiple kernel subsystems. We cover the inner workings of Linux kernel development, exploring everything from how changes get implemented to why its community-driven approach produces such reliable software. Greg shares insights about the kernel's unique trust model and makes a case for why engineers should contribute to open-source projects. We go into: • How widespread is Linux? • What is the Linux kernel responsible for – and why is it a monolith? • How does a kernel change get merged? A walkthrough • The 9-week development cycle for the Linux kernel • Testing the Linux kernel • Why is Linux so widespread? • The career benefits of open-source contribution • And much more! — Brought to by: • WorkOS — The modern identity platform for B2B SaaS. • Vanta — Automate compliance and simplify security with Vanta. — The Pragmatic Engineer deepdives relevant for this episode: • What TPMs do and what software engineers can learn from them: https://newsletter.pragmaticengineer.com/p/what-tpms-do • The past and future of modern backend practices: https://newsletter.pragmaticengineer.com/p/the-past-and-future-of-backend-practices • Backstage: an open-source developer portal: https://newsletter.pragmaticengineer.com/p/backstage — Where to find Greg Kroah-Hartman: • Social: https://social.kernel.org/gregkh • Website: http://www.kroah.com/log/about/ Where to find Gergely Orosz: • X: https://x.com/GergelyOrosz • LinkedIn: https://www.linkedin.com/in/gergelyorosz/ • Bluesky: https://bsky.app/profile/gergely.pragmaticengineer.com • Newsletter and blog: https://www.pragmaticengineer.com/ — In this episode, we cover: (00:00) Intro (02:23) How widespread is Linux? (06:00) The difference in complexity in different devices powered by Linux (09:20) What is the Linux kernel? (14:00) Why trust is so important with the Linux kernel development (16:02) A walk-through of a kernel change (23:20) How Linux kernel development cycles work (29:55) The testing process at Kernel and Kernel CI (31:55) A case for the open source development process (35:44) Linux kernel branches: Stable vs. development (38:32) Challenges of maintaining older Linux code (40:30) How Linux handles bug fixes (44:40) The range of work Linux kernel engineers do (48:33) Greg’s review process and its parallels with Uber’s RFC process (51:48) Linux kernel within companies like IBM (53:52) Why Linux is so widespread (56:50) How Linux Kernel Institute runs without product managers (1:02:01) The pros and cons of using Rust in Linux kernel (1:09:55) How LLMs are utilized in bug fixes and coding in Linux (1:12:13) The value of contributing to the Linux kernel or any open-source project (1:16:40) Rapid fire round — See the transcript and other references from the episode at https://newsletter.pragmaticengineer.com/podcast — Production and marketing by https://penname.co/. For inquiries about sponsoring the podcast, email [email protected].